1. Field of the Invention
The present invention is directed to a class of novel azoles of 5,6-dihydro-1,4-oxathiins and a method for their preparation. More specifically, the present invention is directed to a class of novel azoles of 5,6-dihydro-1,4-oxathiins useful as fungicides.
2. Description of Related Art
The control of phytopathogenic fungi is of great economic importance since fungal growth on plants or on parts of plants, i.e., fruits, blossoms, foliage, stems, tubers, roots, inhibits production of foliage, fruit or seed and the overall quality of the harvested crop.
Plants have long been treated with fungicides to overcome or at least reduce the detrimental effects of fungi. However, the enormous economic toll taken by identified fungi, as well as the development of new fungus strains resistant to known fungicides, establishes a continuing need to develop new and more effective fungicides which possess curative, preventative and systemic action to protect cultivated plants. These new fungicides must not only positively possess these protective properties but, negatively, must not possess properties which have an adverse effect on the plants to be protected.
The use of certain 1,4-oxathiin compounds to provide fungicidally effective compositions is known in the art. For example, U.S. Pat. No. 3,249,499 describes some carboxamido oxathiins as effective biocides, especially systemic fungicides and bactericides. One such compound is 5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxamide as represented by the formula (A): ##STR2##
Also, the use of nitrogen-containing heterocyclic compounds to provide fungicidally effective compositions is known in the art. For example, U.S. Pat. No. 4,202,894 describes a class of heterocyclic compounds, i.e., morpholines, piperidines and the like which are useful as fungicidal agents. Although the compounds of the above discussed prior art disclosures are 1,4-oxathiin and nitrogen-containing heterocyclic compounds, they are characterized by structures which are clearly distinguished from azoles of 5,6-dihydro-1,4-oxathiin.
The rearrangement of 1,3-oxathiolane sulfoxide (B) under acid catalyzed conditions to produce 5,6-dihydro-1,4-oxathiin has been disclosed in U.S. Pat. No. 4,152,334. ##STR3##
The rearrangement described in the present invention for azole containing oxathiolane sulfoxides (II) producing novel and fungicidal 5,6-dihydro-1,4-oxathiin-3-azoles (I) has never been disclosed in the literature. ##STR4##
Intermediates (II) and their precursors (III) have been described in European Patent Publication No. 0224998 published Jan. 18, 1989 as having fungicidal properties. ##STR5##
The above remarks establish that there is recognized a continual need to develop new compounds, distinguished from the compounds utilized in the prior art, to provide a different spectrum of anti-fungal and/or fungicidal activity against the scourage of phytopathogenic fungi.